The central hypothesis of this proposal is that there is an abnormal qualitative and quantitative distribution of gangliosides in malignant gliomas and medulloblastomas, perhaps similar to fetal brain, but different from normal adult tissues, especially normal adult neurons and glia. Biochemical analyses will first characterize and quantitate the types of gangliosides present in a large series of malignant human glioma biopsies, permanent glioma derived cell lines, and athymic mouse and rat-human glioma xenografts and detemine if unique gangliosides are present which are characteristics of gliomas. This methodology will then be utilized to similarly characterize and quantitate the types of gangliosides present in our models of human medulloblastoma. Our specific aims are: a) To produce monospecific monoclonal antibodies directed against the unique D-54 MG mono- and disialogangliosides 3'-iso-LM1, LD1, and GM3, GD3, GM3, GD2 and additional unique gangliosides defined in the course of this study; b) to define the distribution in human glioma tissue of these gangliosides qualitatively at the cellular level using immunocytochemistry with monoclonal antibodies directed against 3'-iso-LM1, LD1, GM3, GD3, GM2, GD2 and each new unique ganglioside and quantitatively at the tissue level using analytic techniques and thin layer chromatography on multiple human gliomas with varying cytomorphologies and degrees of malignancy; c) to use these monoclonal antibodies directed against 3'-iso-LM1, LD1, GM3, GD3, GM2, GD2 and each new unique ganglioside to examine the function of the defined gangliosides in cell-cell interactions, clonogenicity, and invasion utilizing in vitro and in vivo assays of cell growth, adhesion, and invasiveness; d) to use those monoclonal antibodies directed against 3'-iso-LM1, LD1, GM3, GD3, GM2, GD2 or any of the new unique gangliosides exhibiting broad reactivity within and among human gliomas and minimal normal tissue reactivity to demonstrate radioimaging and radiotherapeutic efficacies in the nude mouse - human glioma xenograft model; e) to define similarly the potentially abnormal qualitative and quantitative distribution of gangliosides in medulloblastoma, using the most complete and rigorously characterized models for this tumor extant and to execute similar studies as with gliomas. These studies will, therefore define the biodistribution of the altered gangliosides in human glioma and medulloblastoma, contribute to the understanding of the functional significance of gangliosides in adhesion, growth, and invasion, and establish pre-clinical efficacy of radiolabeled anti-ganglioside antibodies in glioma and medulloblastoma radioimaging and radiotherapy to aid in selecting monoclonal antibodies for clinical trials.